This chapter answers two deceptively simple questions, “How much juvenile crime is there today?” and “How does the level of juvenile crime today compare with juvenile crime 20 or 30 years ago?” The discussion focuses on juvenile crime trends in the U.S. since 1980. Traditionally, researchers answer questions about changing juvenile crime rates with data from law enforcement. According to estimates created from the Uniform Crime Reporting data from the Department of Justice, for example, law enforcement agencies across the United States made an estimated 2.2 million arrests of young people under age 18 in 2007 (Federal Bureau of Investigation 2008). The number of juvenile arrests in 1980, however, was also 2.2 million. Perhaps juvenile crime did not change at all during the past three decades. Is this an adequate answer? Does it tell us all we need to know about the volume of juvenile crime in America, or should we ask for more information?